In a minor news feed design change that appears intended to make stories more diverse and Facebook-focused, the company has begun grouping news feed stories from other apps and sites together.

For example, instead of seeing five tweets from friend who import their messages via the Twitter app to your feed, you’re now more likely to see only one, along with a link beneath it that says “Show 4 similar posts.” If you click on the link, the others will be revealed.

The change applies to both the algorithmic “Top News” view of the news feed (as of last week), along the raw “Most Recent” feed (as of last month). Beyond apps, it affects sites that use Facebook’s Open Graph APIs for user communication.

This might hurt Twitter and other services that revolve around a lot of broadcast messaging through the news feed, such as social games made by aggressive developers. Many apps try to message the stream as much as possible to have users solicit favors from their friends — and thereby engage more people more often. Indeed, a quick Google search shows that a number of devoted social gamers have been creating protests groups and Pages.

The reasons Facebook would implement this change are simple. The company doesn’t want any one third party to dominate users’ news feeds and create a disproportionate amount of news feed content. Instead, it wants a balance of stories coming to users from apps and the web. It also wants to emphasize its own services, like photos, status updates and events — those are not truncated.